Treatment of refractory materials.



E. WEINTRAUB. TREATMENT OF REFRACTORY MATERIA APPLICATION FILED OUT. 27,1909.

Patented July 11, 1911.

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nzncnmr. wnm'rnaus, or LYNN,

MASSACHUSETTS, ASSIGNOR TO GENERAL nLEcrnIc COMPANY, A CORPORATION OIYORK.

TREATMENT OF REFRACTORY MATERIALS.

Specification of Letters Patent. Original application filed December 4,1906, Serial No. 346,258. Divided Patented July 11, 1911. and thisapplication filedOctober 27, 1909. Serial No. 524,948.

To all whom it may concern:

Be it known that I,EznoH1'aL WEINTRAUB, a citizen of the United States,residing at Lynn, in the county of Essex, Commonwealth of Massachusetts,tain new and Serial No. 346,253

S1011 of'm a lication y Pp of which the fol filed December 4, 1906,)lowing is a specification. This'inventlon relates to methods ofpurlfying and treating ofglowers or laments for lamps and fur- Ihav'ehereinafter as applied to the purification and fusion of boron, butthe utility of my invention is not hmited in its application to this onematcrial, but is a generic one as applied to the are treatment ofrefractory conductors.

The usual method of producing boron ineludes the reduction of boricanhydrid with magnesium, the

general process heat a mixture of magnesium with purified, as by washingand fractional decantation. It is in the form of a brown powder,practically non-conductive. for electricity, and

containing magnesium and other lmpurlties,

To secure conductive boron from the material above described, I compressit -into the form of a stick or rod, say six centimeters long and fivemillimeters in cross section, This stick is then highly heated inavacuum to dissociate and drive ofi various of the impurities. For thisheating treatment, I may conveniently utilize the vacuum furnacedescribed in: United States patent to Arsem, No. 785,535, March 21,

1905'. This heat treatment dissociates any present and magnesium boridwhich may be drives off the magnesium; and, in ease-any boric 'anhydrid,3,0,, is resent, that also passes ofl by direct volatihzatiofi. ,Theheat treatment may be continued for several hours at a temperature ofsay 1200 degrees 0., without any dan er of contaminating the boron byvthe car on of the resistance have invented ceruseful Improvements in theTreatment of Refractory Materials, (d1v1-- refractory materials, and 1 llncludes a furnace treatment applicable to r the fusion of boron andother refractory ma teri'als,'such, for instance, as have been producedand are being used in the manufacture 1 the drawing forming quantity ofmercury described the treatment being to an excess 'of'b'oric anhydrid.The resulting product is -pends-a rod or wire 13 heater used in thefurnace above mentioned. purification of the boron by this heating inthe vacuum, but I find that another very important change takes place,and that the stick, which before treatment was a non-conductor, becomesa relatively good conductor of electricity.

' my process COIlSlStSlIl meltby heating it as anode in a vacuum arc.The apparatus for carrying out 'this step is illustrated in part of thisspecification, and is hereinafter described in detail.

-A hermetically sealed envelop 1 of glass is provided at its bottom witha cup-shaped depression 2 capable of holding a suitable for use as thecathode of a mercury are. Suitable lead-wires 3 pass through the glassmeans for connecting the, mercury to a A small tube 4 leads out asoccasionmay require. A suitable stop cock 6 is provided for controllingthe flow of mercury'into this well. A bottomless cup 7 of alumina issecured in the mercury chamber and projects above the surface of themercury, and thereby prevents wandering of the cathode spot over againstthe side of the glass envelop where it might do damage by excessiveheating. The upper endof the glass envelop is connected by a tube 9 witha good vacuum and this tube also gas -may be admitted to the arcchamberafter the latter has been exhausted. pressure gage 11 serves toindicate the mace chamber- 1 desurrounded by-a protective sleeve 14 andsupporting at its lower end a carbon tube or sleeve within the end ofwhich is secured one end of a stick or rod 15 of the material to betreated or melted.

To start the apparatus into operation, I exhaust the main eham er 1 andthe mer- From the top of the envelop and serve as cury well 5 by meansof the vacuum pump, and I then introduce sufiicient mercury throughfunnel 12 to raise the level in the alumina cup 7 until contact is madewith the lower end of the stick 15 to be treated. I next introduce asmall quantity of gas inert with respect to the material to be treated,as I have found that this addition concentrates the are on the lower endof the material under treatment and prevents the tendency which the arcwould otherwise have of running to the lead-Wire 13, this beingparticularly the case if the material is of lower conductivity than thelead-wire. Various gases may be introduced to produce this concentrationof the arc, and in "general, I consider that the eifect is due to theincreased resistance oflered to the passage of the are through thegaseous medium of the envelop, by virtue of which the arc takes theshortest path to the anode and is thereby concentrated on the endthereof. If the stick under treatment consists of boron, I may ushydrogen as the gas; and although the quantity may vary considerably, Iprefer to use hydrogen at a pressure of from two and a half to fifteencentimeters of mercury.

To start the are between the mercury cathode and the solid anode 15, Iopen the stop cock 6 and allow a small quantity of the cathode mercuryto flow through into the well 5, and thereby lower the level of themercury in cup 7 This produces an are which can be drawn out to theproper length by further subtraction of the mercury from the cathode.

The heating action of the-mercury is so intense and so concentrated thatit fuses down the end of the stick into a bead or globule, and I amthereby enabled to obtain relatively large quantities of pure boron in acompact, homogeneous and thoroughly fused mass.

The standard chemical text books describe boron as being anon-conductive material which vaporizes at high temperatures withoutmelting. Such statements in no wise apply to the boron I have producedas above described, for it is a relatively good conductor ofelectricity, is a dense and solid body and undergoes complete fusionwithout apparent vaporization.

In the furnace treatment above described, the introduction of an inertgas to secure cury vapor concentration of the are on the anode undertreatment furnishes an easy means for treatmg boron, but is not limitedin its ap lication to this one material. It has been ound of greatutility in the treatment of that general lass of refractory materials ofwhich boron is typical, such, for instance, as have been produced andare being used in the manufacture of glowers or filaments for lamps andfurnaces. I consider that this step in my process is a generic one, asapfilled to the arc treatment of refractory conuctors.

In my parent application, Serial No. 346,253, claims are made on methodsfor producing boron. In a divisional case, Se-

rial No. 585,391, filed October 5, 1910, claims are made on boron as anarticle of manufacture. In another divisional case, Serial No. 541,155,filed Nov. 12, 1907, renewed J anuary 31, 1910, claims are made on theapparatus herein disclosed. What I claim as new, and desire to secure byLetters Patent of the United States, is- 1. The process which consistsin treating a conductive body as anode in a mercury are operating in aninert atmosphere of sufiicient density to give a prescribed path to thearc.

2. The rocess which consists in melting a conductive body used as anodefor a merarc operating in'an atmosphere of an indifferent gas of a fewcentimeters of mercury.

3. The process which consists in treating a conductivebody as anode in amercury vapor are operating in hydrogen, to chan e gag physicalcharacteristics of said ano e 4. The process which consists in melting arefractory body used as anode for a mercury vapor .arc, operating inhydrogen at low pressure. v

5. The process which consists in melting a refractory element used asanode for a mercury vapor arc, operating in an inert atmos here ofsufiicient density to localize the heating action at the end of saidanode.

In witness whereof, I have hereunto set my hand this 26th day ofOctober, A. D.

EZECHIEL WEINTRAUB. Witnesses:

Joan A. MCMANUB, J r., CHARLES A. BARNARD.

